Screening device and clamp means therefor



Nov. 8, 19 B. D. TONJES ETAL SCREENING DEVICE AND CLAMP MEANS THEREFOR 2 Sheets-Sheet 1 Filed May 1, 1958 H .Nh w NM 3 R N H I F Q INVENTORS: Emu, I]. TUNJES,

BY 12032122 A. EL NE.

Nov. 8, 1960 B. D. TONJES EI'AL SCREENING DEVICE AND CLAMP MEANS THEREFOR Filed May 1, 1958 2 Sheets-Sheet 2 gym-1n- V INVENTORS:

BURL 17. Tazuzs. BY 1205.232" AELI E Unite SCREENING DEVICE AND CLAMP MEANS THEREFOR Filed May 1, 1958, so. No. 732,202 36 Claims. (oi. 209-319 This invention relates to a screening device and tray clamping means therefor. More particularly, it deals with a hydraulic means for clamping a series of screening trays and for holding them in proper alignment on a shaker frame during the shaking process and separation of the materials being screened, and other improvements in the structure and parts of screening devices.

The general nature of shaking devices of the type wherein this disclosure may be most applicable is described in US. Patent No. 2,358,453 issued September 19, 1944, to Seth I. Gilson, which patent described a mechanism for vertically reciprocating a stack of shaker screens or trays and spacers alternating therewith, the stack of trays and spacers being held firmly together in a shaker frame by means of a pair of long manually operated screw clamp rods which also must be manually unscrewed to unclarnp and free the trays for removal from the device after the shaking has been completed.

It is a primary object of this invention to improve the construction of such a device and to simplify the operation thereof, thereby producing an efficient, simple, effective, economic, relatively quiet, and self-contained screening device.

Another object is to provide for such a batch type screening device having a vertically reciprocating shaker type mechanism, a relatively quick acting, positive, eflicient, and economic hydraulically actuated screen tray clamping means, and a manually operated combined bydraulic pump and valve assembly unit arranged to supply, control or release fluid pressure through flexible ducts to or from the clamping means.

It is another object to provide in an hydraulic fluid cylinder clamping means a construction requiring only one fluid seal.

It is another object to provide such an hydraulic clamping unit as a packaged kit for replacement of the screw type unit for the screens of the device of the aforementioned patent.

, It is another object to provide an anti-spill bevel insert for the shaking trays of such a device and still maintain viewability into the tray.

It is another object to provide bearings in some of the actuating elements of the mechanism so as to eliminate the need for application of grease and thus not only prevent accumulation of dirt in the bearings but also to prevent contamination of material being screened.

It is a still further object to provide a quickly removable dust cover for the front and top access openings in the frame to minimize the spreading of dust clouds during use of the device.

It is a still further object to provide a sound deadening or acoustical insulation material in the cabinet to obtain a more nearly quiet operation of the device.

In general terms, this disclosure comprises a vibratory screening device having a stationary main frame, a shaker unit in said main frame, a drive unit for shaking said shaker unit, and means for clamping trays of aggregate to be screen in said shaking unit. Preferably the stationary States Patent ICC main frame is enclosed and preferably noise insulated With removable covers for access to the shaker unit. The shaker unit comprises upper and low sub-frame members, one or more, preferably non-spilling, screening trays and tray spacing members stacked alternately between the trays for maintaining a spaced relation between the trays, and a pair of guide clamp rods mounted at two opposite sides of said trays and spacers adapted to grip and firmly clamp a stack of. trays in vertically aligned relation in the shaker unit as well as guide the unit: for vertical reciprocation in the main stationary frame. 7

An important improvement comprises vertically mounted fluid operated piston means adapted to actuate the clamping means, and a pair of cylinders mounted on the upper sub-frame member adapted to enclose said pistons, the clamp rods being secured at their upper ends to the pistons and their lower ends being adapted to engage the lower sub-frame member for clamping. the trays in stacked relation in the shaker frame. The improvement also comprises a reciprocating pump means on the stationary frame, a manually operated piston and valve passages in the pump body having connections arranged in such a manner that pressure developed by the pump means may be transferred and maintained through flexible ducts to the clamp cylinders and clamp rods associated therewith, then on completion of the shaking operation an extra manual movement of the piston in the pump may unseat a spring loaded check valve to release a by-passage in the pump body to free the oil or fluid pressure within the two clamp cylinders and permit return of the fluid into the pump reservoir. Spring means mounted within the clamping cylinder and acting against the clamp piston may be supplied to augment the force of gravity in unclamping the trays. This hydraulic clamping system also is designed so as to be supplied as a unit kit for replacing other and manual clamping units on such shaking or screening devices.

The above mentioned and other features and objects of this invention and the manner of attaining them will become more apparent and the invention itself will be understood best by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:

Fig. 1is a sectional elevation of a vibrating screen type shaker showing the main drive mechanism and embodiment of the hydraulic clamping cylinders for the device;

Fig. 2 is a cross-sectional view taken along lines II-II on Fig. 1 illustrating the drive mechanism and interconnecting parts associated with the screen unit, together with a manually operated reciprocating pump unit associated therewith;

Fig. 3 is a detailed sectional view similar to Fig. 1 with parts broken away, illustrating the manner in which the screen trays may be gripped by the spacer means in the shaker unit and how the clamp rods may be actuated through their connection to the piston in the clamping cylinder;

Fig. 4 illustrates a fragmentary perspective view of a portion of a screen tray and its frame construction with an anti-spill shield mounted in the frame;

Fig. 5 is an enlarged detailed cross-sectional view of the upper right corner portion of the main frame and upper sub-frame elements shown in Fig. 1, illustrating the bearing means and sleeve guide means for the clamp rods as mounted for vertical vibratory movement in the main frame;

Fig. 6 is an enlarged sectional view taken along line VIVI of Fig. 1, showing the clamp rod and actuating cylinder assembly and their mountings and relative movement in dotted lines, with respect to the main frame;

Fig. 7 is a plan section along the line VII-VII of Fig. '6;

Fig. 8 is an enlarged detailed partially cross-sectional view of the pump assembly of Fig. 2, showing parts therein, including a reciprocating piston and some of the valve means for operating the clamping units;

Fig. 9 is a cross-sectional plan view taken along line IXIX of Fig. 8; and

Fig. 10 is a fragmentary cross-sectional view along the line X-X of Fig. 9 illustrating the pump supply connection from the reservoir and some of the related connections in the pump body.

I. General arrangement In the sand and gravel industry along with others such as coal, ore, cement, etc., in which mixtures of coarse and fine aggregate need to be separated in order to determine percentages of fines as relatd to coarse parts in a sample to be tested, a shaker type screen is very commonly employed. In general a device of this type is shown in Figs. 1 and 2 and consists of a frame 12 mounted on legs 14 which may be bolted to a floor for stability, and in a level manner for equalizing the distribution of the mixtures on the screens. Side panels 15, 16 and rear panels 17 may be provided to enclose the frame 12, the front 18 of the frame usually being left open to provide access to the interior when loading and unloading a stack of screen trays for a screening operation in the machine. The bottom of the frame 12 may be closed by a panel 19, and the top panel 20 therefor may be provided with an opening 21 for accessibility to the shaker unit when supplying the screens with samples of aggregate to be separated. A removable cover panel or door 22 may be provided to cover the top access opening 21, and a handle 23 may be provided thereon for convenience in placing or removing the cover. A similar removable cover 24 may be provided for the opening in the front 18. Both covers 22 and 24 may be connected along adjacent edges by a hinge having a pin connection 25. Thus, both covers 22 and 24 may be removed simultaneously from the machine when trays "are to be removed or replaced and samples of aggregate are to be tested. Clips or permanent magnets 26 (see Fig. 2) may be provided to hold the front cover 24 against the opening 18 if so desired.

A drive unit 27 may be mounted on the top panel 20 and may consist of a motor 28, having a belt connection 29 to a sheave 30 which is mounted on a transverse counter shaft 31 for providing a reciprocatory motion for the shaker unit; a control switch 32 being provided to start and stop the drive motor 28. The control switch 32 may also include a timer for controlling the shaking period for the device. The drive mechanism may comprise the shaft 31 journalled in a bracket member 33 adjustably mounted by means of adjusting screws 34 on a mounting plate 35 also mounted on the cover panel 20. The ends of the shaft 31 may be provided with eccentric extensions 36 carrying connecting rods 37 for attachment to a shaker unit presently to be described, and to provide a means for vertical reciprocation thereof within the frame 12.

If desired, the inside of the wall panels 15, 16, 17 and 20, and the cover panels 22 and 24, and preferably the outside of bottom panel 19 may be coated or covered with a sound deadening material 39, such as a fibrous material sprayed on or otherwise attached thereto.

II. Shaker unit Within the frame 12 there may be mounted a bank or stack of trays and tray spacers or support members which are caused to vibrate collectively in a vertical reciprocatory manner. A suitable construction for a shaker unit 40 of this type may consist of a steel structure fabricated in such a way as to make an open sided rectangular generally box-like shaking frame consisting of an upper and lower closed rectangular frame element 41 and 42 respectively, and a plurality of loose intermediate U shaped frame elements 43, the lower frame element 42 being provided with a vertically offset cross tie member adapted to permit passage of a tray thereover. The upper frame element 41 is normally suspended at its four corners by bolts 44 having loose contact with the upper frame member 41 and held substantially equally spaced from the corners of the frame 12. The upper frame 41 is supported and in fact is suspended on a pair of screw studs 45 which may pass through openings 46 in the lower ends of the connecting rods 37, the studs 45 being threaded into brackets 47 on the shaker frame 41. The openings 46 in the connecting rods 37 may be provided with nylon bearing bushings 48 which act as dry bearings for the studs 45 thus requiring little or no lubrication. The frame thus is elevated slightly from the heads of the bolts 44, and may bear against a set of force balancing springs 49 enclosing the bolts 44. As a result of the action of the eccentrics 36 on the connecting rods 37, the shaker frame 40 may be caused to vibrate in a vertical reciprocating manner, the bolts 44 and springs 49 acting as guides and stabilizers for the frame 40.

When assembling a device of this type a plurality of screen trays 50 and spacer frame elements 43 may be stacked alternately one above the other as viewed in Figs. 1 and 2 in a manner so that the coarsest or largest opening screen will be at the top of the stack and the finest or smallest mesh screen will be at the bottom of the stack. A pan 52 may be located below the screen trays 50 and supported on lower frame element 42 to collect siftings and fine particles passing through the lowermost screen 50. Furthermore, a pan 52 may be placed directly on the bottom panel 19 in the event it is desired to use an additional screen tray on the frame element 42. Each of these trays 50 and pan 52 may be withdrawn from the open side of shaking device 40 through the front opening 18 in the frame 12. The spacer elements 43 may be in the form of U-shaped channel sections following generally the conformation of the left side panel 15, the rear panel 17, and right side panel 16, as illustrated in Figs. 1 and 2. The edge flange sections of the channels 43 and frame elements 41 and 42 may have openings 54 (see Fig. 6) for passage therethrough of a pair of clamp rods 55. The clamp rods 55 may have a pilot connection at the bottom of the frame 12 through guide bearings 56 mounted below the lower inturned edge of the side panels 15 and 16. The upper ends of the clamp rods 55 may be passed through similar bearing guides 58 mounted on the top panel 20 of the frame 12, however, these latter guides 58 may be of a larger bore to accommodate a sleeve construction associated with the clamp rods 55 to be described hereinafter.

The screen trays 50 and their spacer frame elements 43 ordinarily may be carried in the frame 12 when in spaced apart arrangement as indicated in Fig. 1, by either separate rods 23 with stops 27 as shown in the above mentioned Gilson patent, or by support lugs 59 shown in Figs. 1 and 3 herein provided in the side walls 15 and 16. These stops or lugs 59 support the unclamped elements 43 in a predetermined spaced relation to provide an initial space 60 between the spacer elements-43 to facilitate loading and unloading of the trays 50 within the chamber of the shaking frame 40 in stationary main frame 12. When the clamp rods 55 are raised in a manner to clamp the parts in their clamped positions as shown in Fig. 3, the spacer frame elements 43 are elevated from the support lugs 59, each in turn being lifted, until a compact clamped arrangement of the trays and spacers is attained to form the shaker unit 40. For this purpose the clamp rods 55 may be provided with stop collars 61 which may be fixed to the clamp rods 55 by means of pins 62, upon which collars 61 the lower frame 42 rests which also supports the pan 52.

The shaker screens o-r trays 50 may be formed of side wall elements 64 having outwardly extending flange portions 65 and inward flanges 66 as illustrated in Fig. 4.

aerate-e Wire mesh 67, or other screening material used in devices of this character, may be placed across the open area bounded by the flanges 66 of the frames 50, and clamp plates 68 held in place by bolts 69 may be provided to hold the screen 65 firmly in place in the tray. The forwardly extending portion of the trays 50 may be fitted with handles 71 for convenience in handling the trays while they are being moved in or out of the shaker compartment or frame 40. Ordinarily there may be a slot like gap or opening existing between the trays at this forward area, since the U-shaped spacers 43 are not carried across the forward wall of the shaker assembly 40.

A device for preventing spillage over the forward flanged edges 70 of the trays 50 adjacent the opening 18, during the vibration period may be provided in the form of a shield 72 having a downwardly and inwardly inclined projecting flange portion 73 and a downwardly extending flange portion 74 for insertion between the side wall member 64 of the tray 50 and the clamp plate 68 therein. Thus, when the trays 50 and spacers 43 are clamped solidly together (see Fig. 3), they form a substantially closed chamber along the two side wall portions 75 and rear wall portion 76, and the front wall has the protection of the above mentioned devices 72 for preventing spillage from the individual trays during the shaking operation.

III. The clamping device and fluid pump mechanism The clamp rods 55 are mounted for slidable movement in the openings 54- of the flanges of the spacer units 43 and through a flange of the upper sub-frame member 41, thence through openings in the upper frame 20 (see Figs. 5 and 6) as previously described. However, the upper portions of the rods 55 may be passed through sleeve members 77 which act as spacers or extensions between the upper frame element 41 of the frame member 40 and the head flanges 78 of a pair of fluid cylinders 80 to complete the clamping circuitsbetween the piston rods and the cylinders 80. Thus, the sleeves 77 slide up anddown through the top panel 20 of the main frame 12, the entire clamped together unit, with the cylinders 80 reciproeating with the shaker frame 40. A wear plate 79mg be provided on the upper and lower frame elements 41 and 42 to reinforce the area of contact of the sleeve 77 and stop collars 61. r I '1 Each cylinder 80 (see Fig. 6) may comprise a chamber 81 closed by a cap 82 at its upper end. Thehead flange portion 78 may have a bore 83 to receive one end of the clamp rod 55 therethrough. At the upper end of the clamp rod 55 there may be placed a specially formed cup'shaped piston member 85 having a centralhub portion 86 fixed to a shoulder 87 at or near a threaded end of the rod 55. A set nut 88 may be provided to secure the piston 85 to the rod 55. The piston 85 compi ises a skirt portion 89 depending from the hub portion 86 to terminate in a flanged edge 90 to carry a compression spring 92 thereon normally urging the piston 85 and the clamp rod 55 downwardly in the cylinder chamber 81. Only one oil seal ring 93 need be provided to seal the piston 85 with the inner wall surfaces of the cylinder 80 against the leakage of fluid upwardly into the chamber 81. Each cylinder head 78 may have an upwardly directed sleeve-like extension 94 concentric with the cylinder 80 and cup-shaped piston 85 to provide a sealing surface 95 on the inner diameter of the oil seal 93 for preventing leakage of fluid downwardly along the clamp rods 55. The extensions 94 may reach approximately one half the length of the cylinders 80 to provide sufficient sealing surface during the stroke of the pistons 85 within the chambers 81. An hydraulic fluid or oil port 96 may be provided in each cylinder head 78 to provide communication from a pair of flexible oil ducts 98, 99 110 move the pistons 85 and seal rings 93 upwardly in the cylinders 80 to raise the clamp rods 55 simultaneously to tray clamping position as shown in Fig. 3".

A-p ump 100may be adaptedto deliver fluid pressure to the cylinders through flexible ducts 98 and 99, the fluid under pressure being supplied simultaneously from the pump to each of the cylinders 80 and preferably to the space 101 below the seal rings 93 in the cylinders. The pump 100 comprises a reservoir portion 102 (see Figs. 8,9 and 10) formed within side walls 103, 104, rear wall 105 and front wall 106. A bottom portion 107 may be formed with various passages and bores for accommodating a piston and set of valve parts for establishing fluid pressure for the system and for conducting the fluid pressure through a system of channels and ducts into the cylinders 80 for the purpose of clamping or unclamping the screen trays 50 between the spacer elements 43. The pump body 100 may have mounting feet 108 adapted for attachment to the top panel member 20 of the main stationary frame 12. I p

The bottom portion 107 of the pump body 100 may be provided with a bore 110 to receive a piston 111 adapted for horizontal reciprocatory motion therein, a piston rod 112 being extended through a packing gland 113 in the bore 110 to provide a fluid sealing means for the piston rod. A link 114 may be provided to connect the outward end 115 of the piston rod 112 to one end of a rock lever 116 having a fulcrum connection 117 between a pair of cars 118 mounted on the front wall 106.

of the pump body 100. An upwardly extending arm 119 of the rock lever 116 may be operated in a rocking motion to cause reciprocation of the piston 111 in the bore 110. In an ordinary pumping operation the arm 119 may be moved to the 119' position to cause the piston 111 to move toward the left in the bore 110 (see Fig. 8) to create a negative pressure in the pump chamber 120 and thereby draw a charge of fluid from the reservoir 102 into the said chamber 120 in the bore 110 to constitute a suction stroke for the pump. A drilled passage 121 may lead from the chamber 120 in a horizontal direction toward the right in Fig. 8 to transverse bore 122 in the pump body (Fig. 10). A check valve 123 maybe provided in the bore 122 to normally seal a duct 124 communicating with a vertical downwardly directed duct 125 from the reservoir 102. Thus, when the piston 112 is moved toward the left to produce a suction stroke, fluid will be drawn downwardly through the duct 125 into the duct 124 to unseat the check valve 123 and proceed into the duct 121 to enter the chamber 120. p

When the handle or lever 119 is moved now toward the left, or full line position of Fig. 8, the piston 112 will be caused to move again toward its full line position at the right of the stroke to develop a positive pressure in the chamber 120. This pressure will be sealed against return passage through the duct 124 by the check valve 123 due to the initial influence of a compression spring 126 acting normally against the valve 123. However, the fluid will pass downward through a port or duct 130 against the relatively low spring pressure on a check valve 131, and may now enter a passage 132 leading forwardly in the base of the pump body 107 to a pair of connections 135 and 136 to the flexible conduits 98 and 99 for distribution to the cylinders 80. Fluid pressure thus conducted to the cylinders 80 will raise the pistons 85 therein together with the clamp rods 55 attached thereto; the screen trays and spacers thus being clamped firmly as a unit in the shaker frame 40.

After a shaking operation has been completed and it is desired to unload the cylinders to unclamp the trays for removal from the shaker machine, there may be provided a valve unloading means 140, for automatically releasing the fluid pressure Within the cylinder 80. To operate valve 140, as shown in Fig. 8, the handle or lever 119 may be moved slightly farther to the left against the action of a spring 139 to dash-line position 119", thus moving the piston 111 slightly farther to the right at which time the end of the piston 111 may contact the end of a valve unloading pin 141 in the pump body. This extra motion acts to unseat a check valve 142 in a bore 143 normally held in closed position by a relatively high pressure compression spring 144. A communicating passage 145 may be provided to connect the ducts 132 and bore 143 with an escape duct 146 in the pump housing, to permit return of fluid from the chambers 101 under the pressure of springs 92 in the cylinders 80, through the flexible ducts 98, 99, and ducts 132, 145 and 143, unseated check valve 142, and duct 146, back into the reservoir 102. The check valve 142 normally remains closed throughout the usual pumping operation for clamping the trays, due to the relatively high back pressure being applied by the spring 144 on the valve 142, and thereby tends to force the flow of fluid from the pump chamber 120 downwardly through the check valve 131 into the duct 132 for distribution to the clamp cylinders 80.

As the trays are being clamped securely together and the flow of fluid being pumped into the clamp cylinders is being resisted by the gradual closing together of the trays and the system becomes stable the flow is stopped and all of the check valves may then become closed automatically, maintaining pressure in the cylinders 80 throughout the shaking operation and until this pressure is released. However, there may be provided an unloading valve 150 for the pump, normally held closed by a relatively high pressure compression spring 151 seated in a threaded bore 152, the spring pressure being regulated by means of an adjusting screw 153 and set nut 154 therefor. An escape port 155 may be provided in one side of the bore 152, to permit flow of fluid therethrough into the reservoir 102 when unloading of the system is desired. For this purpose the handle 112 while being moved to the extreme left position as at 119 causes a temporary increase in the pressure in the pump chamber 120, the pressure being caused to rise sufficiently to open the valve 150 and permit the escape of fluid from the pump chamber upwardly through the port 155 to free the piston 111 for further movement in the bore 110, thus permitting the piston to contact the pin 141, resulting in opening of the valve 142, and immediate release of the fluid pressure in the clamp cylinders 80 to unclamp the trays.

IV. Operation This device may be used in a manner similar to the previously mentioned Patent No. 2,358,453 to Gilson or to other devices of a similar character used in separating samples of aggregate in the sand and gravel, coal mining, etc., industries. The covers 22 and 24 first may be removed from the frame 12 after which the various trays 50 may be removed for arrangement in a predetermined or particular order, preferably one in which a screen tray 50a (see Fig. 2) of relatively coarse mesh screen may be located at the top of the shaker unit, the other trays 50b, 50c, 50d, She having graduated screen sizes approaching smaller and smaller dimensions; the bottom screen 50a ordinarily being of the order of 100 mesh size. The pan 52 at the bottom of the unit may be provided to collect the fine particles passing through the smallest size screen, each succeeding screen in turn supporting the percentage of aggregate not passing through that screen. Then the cover 24 may be replaced and fastened by the clips or permanent magnets 26, the top cover 22 remaining in an open position as shown by dash lines 22' (Fig. 2).

When the trays are loaded between the spacers 43 in the prearranged order and ready for clamping into shaking position, the lever 119 is rocked about its fulcrum 117 to pump fluid pressure into the distribution ducts 98 and 99 to raise the pistons 85 in the clamp cylinders 81), thus elevating the clamp rods 55 and clamping the shaker trays firmly in place between the spacers 43 into normal operating position for vertical vibration in the shaker, by the action of the eccentrics 36, connecting rods 37 and their screw stud connections 45 with the upper element of the frame 40 (see Fig. 3). The control switch 32 may be operated to start the operation of the motor and vibrating unit.

A sample of mixed aggregate up to approximately one cubic foot volume for this type of shaker may now be passed through the opening 21 in the top 20 of the shaker device, the mixed aggregate falling onto the screen mesh 67 on the topmost tray 50a. The top cover 22 may now be closed and as the shaker unit 40 vibrates in the aforesaid vertical direction the particles are bounced and jounced on the top screen until only the largest size pieces remain thereon. As the smaller sized pieces gradually fall through the successive screen trays, each screen in turn supports its percentage of aggregate not passing therethrough. This briefly constitutes a screening operation, the time cycle for which may be determined by experiment, a time control switch in the control 32 being set accordingly. Samples with very small percentages of fines may be screened in a relatively short time whereas samples having higher percentages of fine particles may require a slightly longer time for complete screening through the finer mesh screens. Upon completion of the shaker operation the control switch 32 may cause the drive unit to stop at which time the clamping device may be unclamped to release the trays from their gripped position between the spacer elements 43. The cover elements 22 and 24 may now be removed and the unclamping operation for releasing the trays 50 may be simply done by moving the handle 119 to its dotted line position 119" whereby the unloading pin 141 may act to release the check valve 142 to unload the clamp cylinders 80, thus freeing the trays for removal from the shaker unit.

With this improved construction the shaking time per sample may be shortened, a more convenient clamping procedure is provided, and the device may operate more dust free and more quietly. Furthermore a transparent cover may be provided and installed over the opening 18 so that visible inspection may be had of the shaking progress, the shields 72 being downwardly inclined so that an observer may view the shaking process by looking through such a transparent doorway and through the gap provided between the trays 50 along their forward edges.

While there is described above the principles of this invention in connection with specific apparatus, it is to be clearly understood that thi description is made only by way of example and not as a limitation to the scope of this invention.

What is claimed is:

1. In a screening device having a main stationary frame, a screening unit suspended from the top of said main frame for vertical reciprocatory movement, means located at the top of said main frame for vertically reciprocating said unit, said unit comprising upper and lower sub-frame members, screening trays in the unit, and tray clamping means for the unit; the improvement comprising: fluid operated piston means adapted to actuate the clamping means; a cylinder mounted on said upper sub-frame member adapted to enclose said piston, said clamping means being secured to said piston and to said lower frame member, whereby alternate movement of the piston will actuate the clamping means to alternately grip and release said trays, flexible pressure delivery means associated with the cylinder; an hydraulic pump means on the main frame adapted to alternately supply and release fluid pressure to said cylinder through said flexible delivery means; and resilient means in the cylinder adapted to move the piston when said fluid pressure is released.

2. A device according to claim 1 including tray spacing members stacked alternately between said trays wherein said clamping means also clamps said spacing members with said trays.

3. A device according to claim 1 wherein said means for reciprocating said unit includes non-lubricatable bearifi' sts revnt contamination with lubricants at me products being screened as well as contamination of the bearings with the particles of the products being screened. 4. A device according to claim 1 wherein said means for reciprocating said unit comprises a shoulder bolt means connected to said unit, a motor for rotating an eccentric mounted on said stationary frame, and a link between said bolt means and said eccentric. 5 A device according to claim 1 including panel means attached to said main frame for enclosing said screening unit therein.

A device according to claim 5 including sound deadening material mounted on said panelmeans.

7. A device according to claim 5 including means for removably mounting said panel means along at least one side of said main frame for access to said screening unit. 8. Amachine for screening mixed aggregates having a main stationary frame structure; a drive means mounted on the frame, a screening unit supported in the said main frame and being adapted for independent vertical reciprocation by said drive means, said screening unit comprising; a plurality of removable screening trays, a plurality of tray spacer elements stacked alternately between the said trays, top and bottom clamp elements adapted to support the stacked trays and spacer elements of the unit, a pair of p ull rods adapted to engage the bottom clamp element, a pair of fluid cylinders mounted above the top clamp element, pistons within the cylinders attached to the pull rods, and fluid pressure means mounted on the main stationary frame for actuating the pistons in the cylinders to clamp the trays and spacers rigidly together in the screening unit.

9. A machine according to claim 8 wherein said fluid pressure means comprises one manual reciprocating pump means, and a pair of flexible ducts connecting the said pump means to the said cylinders.

10. A machine according to claim 9 wherein said pump means comprises automatic valve means for maintaining fluid under pressure in the cylinders.

11. A machine according to claim 9 wherein said pump means comprises a manually operated lever for operating said pump, and a pressure unloading valve for releasing the fluid pressure in said cylinders.

12. A machine according to claim 11 wherein said unloading valve is operated by a movement of the manually operated lever.

13. A machine according to claim 8 wherein said flexible ducts are connected to the end of said cylinders adjacent the end that said pistons are attached to said pull rods, and single gasket means between said piston and said cylinder.

14. A machine according to claim 13 wherein each said cylinder comprises an internally extending sleeve through which its piston rod extends; said piston comprises a cup-shaped member fitting over said sleeve whereby only one gasket member is required between the outside of said sleeve and the inside of said cylinder and said piston.

15. In a screening device having a main stationary frame, a screening unit suspended from the top of said main frame for vertical reciprocatory movement, means located at the top of said main frame for vertically reciprocating said unit, said unit comprising upper and lower sub-frame members, screening trays and spacing members stacked alternately between said upper and lower sub-frame members, the improvement comprising: a hydraulic clamping means for clamping said trays and spacing members between said upper and lower frame members, said clamping means comprising: cylinder means adjacent one of said sub-frame members, a piston rod from said cylinder extending to the other of said sub-frame members, a hydraulic pump means mounted on said main frame and attached by flexible fluid duct means to said cylinder means on said screening unit, and resilient means mounted in said cylinder means for noralkali lng', we sub-frames apart for release" of s, d trays between said spacing members in said screeningu'nit. 1 y i I I A system eenrdin to claim 15 including extensi'ohson saidpi'ston rod and guides in said main frame for guiding the movement of said piston rod and said unit in said main frame.

17 system according to claim 16 including sleeves on said rodfe'xfehsioiis between said one of said subfr'amesand said cylinders comprising said guides in said mainframe. v, Y

l8. A'system acebrding to claim 15 wherein said pump means cbmpiises a reciprocating piston and a release valve means operated by said piston in one limiting positionfof its travel. p g V 19'. device a ording" to claim 15 wherein said flexib le duct means err is said cylinder means at the same endthe'reof th'a said piston rod extends from said cylinder means, and a single gasket means between the piston in said cylinder means and the side walls of said cyl nder; man 7 2Q. A i ding toclaim 19 wherein said cylinder means comprises a sleeve extending inwardly from said one end thereof and its piston comprises a cupsliiped member extending over said sleeve, said gasket areal-mare edge of said cup-shaped mem- I Y iiul'a'r chamber between the inside wall of said cyl de means and the outside wall of said sleeve, satdradgareaas bfemg connected to the bottom of said ciip-fs'hapedmefnber; and extending through said sleeve. m 21. devi accdrding to' claim 15 wherein said pump means comprises check valve means for limiting the fluid pressure in said system.

22. In a screening device having a removable screen tray means, means for shaking said tray and means for clamping said tray in said shaking means, said clamping means comprising: an hydraulic pump unit, reciprocating means for operating said pump unit, an hydraulic cylinder and piston associated therewith mounted on said shaking means and adapted to actuate said clamping means to tray clamping position, flexible fluid duct means connecting said pump unit with said cylinder, a clamp rod extending from said piston, a tray engaging means on said rod, another tray engaging means on said cylinder, and resilient means in said cylinder to normally urge said piston towards its tray unclamped position.

23. A device according to claim 22 including by-pass valve means operated by said reciprocating means for releasing the hydraulic pressure from said pump unit to permit said resilient means to unclamp said tray and to return the fluid to said pump unit.

24. A device according to claim 22 including guide means on said screening device for controlling the movement of said shaking means.

25. A device according to claim 24 wherein said clamp rod includes extensions for sliding in said guide means.

26. A device according to claim 22 wherein said hydraulic pump unit and clamping means is independent of the means for shaking the trays.

27. A system according to claim 22 wherein said cylinder comprises an inwardly extending sleeve in one end thereof, said piston rod extends through said sleeve, said piston comprises a cup-shaped member connected to the end of said piston rod, said piston extends around said sleeve in said cylinder, and a single annular gasket means between said sleeve and the inner walls of said cylinder, said flexible duct means being connected to said cylinder at the end adjacent said sleeve.

28. A replacement screen tray clamping attachment for a screening device comprising: a manually operated fluid pressure means, fluid cylinder means flexibly connected to the fluid pressure means, piston means within the cylinder, a clamp rod having one end attached to the piston, the other end having a tray engaging stop attached thereto and adapted to extend below said tray,

a sleeve means on the rod to be located between the cylinder and the top of said tray, and guide bearing means adapted for mounting on the screening device to guide said clamp rod and said sleeve to permit vibratory motion of the screen tray in the screening device, while said screen tray is being clamped between said stop and said sleeve.

29. A replacement attachment according to claim 28 in which the fluid cylinder means comprises resilient spring means for actuating the piston to release the clamp rod when the fluid pressure in the cylinder is released.

30. A replacement attachment according to claim 28 in which said fluid pressure means comprises a reciprocating pump unit.

31. A replacement attachment according to claim 28 in which said fluid pressure means comprises a manually operated reciprocating piston pump unit.

32. A replacement attachment according to claim 31 comprising a manually operated pressure release means in said pump unit.

33. A replacement attachment according to claim 32 in which said pressure release means is responsive to a predetermined movement of a reciprocating part in said pump unit.

34. In a screening device having a removable screen tray, means for shaking said tray, and means for clamping said tray in said shaking means, said clamping means comprising: an hydraulic pump unit, reciprocating means for operating said pump unit, an hydraulic cylinder and piston associated therewith mounted on said shaking means and adapted to actuate said clamping means to tray clamping position, flexible fluid conducting means connecting said pump unit with said cylinder, a clamp rod attached to said piston, one tray engaging means on the rod, another tray engaging means on the cylinder, resilient means in said cylinder to normally urge said piston towards its tray unclamping position, gasket means in said cylinder to seal the relatively movable adjacent surfaces between said piston and said cylinder, and by-pass valve means operated by said reciprocating means for releasing the hydraulic fluid pressure from said pump unit to permit said resilient means to unclamp said tray and to return the fluid to the pump unit.

35. A device according to claim 34 including guide means on said screening device for controlling the movement of said shaking means.

36. A device according to claim 8 wherein said stationary frame structure includes side members, and a plurality of supporting means on said side members for holding each of said tray spacer elements in spaced relationship when said clamping elements are released, permitting the individual withdrawal of any tray or trays.

References Cited in the file of this patent UNITED STATES PATENTS Re. 18,530 Munro July 19, 1932 1,685,018 Bowmaster Sept. 18, 1928 1,725,511 Flanagan Aug. 20, 1929 1,922,986 Stith Aug. 15, 1933 2,193,954 Warner Mar. 19, 1940 2,358,453 Gilson Sept. 19, 1944 2,723,751 Conkling Nov. 15, 1955 

